Author
Topic: Zeppelin Bend: Security and Strength (Read 40519 times)

I'm very new to knot tying. I'm interested in loops at the moment, and in the zeppelin loop in particular. We have xarax's opinion; I'm wondering what others think about the effect of loading one of the ends of the zeppelin bend in forming the loop. Does that make it a less-secure knot than the bend?

I don't recall X. opining this, but simply thatthe symmetry of the end-2-end knot's loadingis lost in the eye knot (as one overhand partis loaded on both ends, the other not).

Quote

I'm also wondering how the zeppelin bend and loop compare in securityto bends and loops typically used in rock climbing. Is there evidence to say definitivelythat the zeppelin bend and loop are or are not to be trusted with my life?

Rockclimbers use end-2-end knots in just a couple ofcirucumstances : joining ends of a small line or tapeto form a closed-loop sling; joining abseil ropes together.In neither of these cases would one have good reasonto favor the zeppelin bend.

Eye knots are used for tying in, and the zeppelin eye knotwill suffice, as will many many others. Its ease of UNtyingafter being loaded is one attractive aspect --but one sharedby numerous bowlines and other lesser known knots.

Dan_Lehman, I have a number of follow-up questions to your reply, but they go outside the topic of this thread. I'd be grateful is you'd reply to a new thread I started: http://igkt.net/sm/index.php?topic=3810.0.

... I'm wondering what others think about the effect of loading one of the ends of the zeppelin bend in forming the loop. Does that make it a less-secure knot than the bend?

Actually, the loop is more secure. Just as the bowline is more secure than the parent sheet bend, most loop knots are more secure than their parent bend. In a loop, one more part of rope is imparting tension into the knot form which usually keeps things more snug. In some loops this may contribute to making the knot harder to untie, but in the Zeppelin Loop, ease of untying is maintained.

Quote

I'm also wondering how the zeppelin bend and loop compare in security to bends and loops typically used in rock climbing. Is there evidence to say definitively that the zeppelin bend and loop are or are not to be trusted with my life?

The Zeppelin Bend and Zeppelin Loop can be trusted with life. In fact they or their double form would be my first choices. And I've gotten positive feedback from people who use them in such capacity.

The Zeppelin Loop is also quite nice in handling oddball loading configuration, such as accidental pulling of the free end, or loading the legs in opposite directions (the latter being something a Figure 8 Loop can have problems with). I also like the distinctive, symmetric knot form makes the Zeppelin Loop (and bend) very easy to check for errors, even from a distance.

I do think that the double/triple fisherman knots are the gold standard of security, it's just unfortunate that they're also horribly jam-prone.

The most important thing is that you are testing knots yourself in the material that you will be using. There is no substitute for this. It will give you a feel for the properties of knots that no amount of reading will do.

« Last Edit: February 29, 2012, 05:51:30 PM by roo »

Logged

If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".

1. The Sheet bend IS NOT the parent of the bowline ! In fact, it has a very limited relation with the bowline, if any. Read the thread "What defines a bowline" (1), about what the bowline is...

2. I have seen no tests of the security or strength of any of the two forms of the Sheet bend, in comparison with any of the two forms of the bowline - tied with/on the same material. While this claim sounds reasonable, I would never trust another person s life on something that, although reasonable, is not tested experimentally.

No, they can not, and they should not ! - until they are tested, and proven to be more secure and strong than any other similar knots that can possibly be used for the same purpose. Of course, I am speaking about other people s lives, ( OPL), because, if anybody actually believes in this, he can always put his own life into test - falling from a increasingly dangerous height above the ground.

I also like the distinctive, symmetric knot form makes the Zeppelin Loop (and bend) very easy to check for errors, even from a distance.

For the so-called "Zeppelin loop", such a distance is a prerequisite...The more the distance, the more 'distinct, symmetric form" this ugly monster acquires. At a sufficient distance, this tangle will be transformed into a perfect circle. However, as a knot, it always remains a zero.

The loop or coil of the Sheet bend most certainly "nips" the U shape of the rope. The distal part of the U shape helps anchor that coil so that it can provide nip.Or would you like to claim that a bowline ceases to be a bowline as soon a rotating, high-friction load causes only the leg belonging to the U shape to be loaded?

We have been talking about all those things, and then some, on the thread about bowlines (1). The question about the relation of the Sheet bend and the bowline, if any, has been discussed by an exchange of different views between Derek Smith and me. I have to remind you that you have vigorously insisted that this was not a "practical" matter, and you orchestrated the head to be removed from the "Practical knots" Forum, to the now extinct "Knot Theory"(!?) Forum.. I would be glad if you have made up your mind by now, wish to read what was written there, and reply THERE.( Many things "nip"other things, but they are not nipping loops ! )

The loop or coil of the Sheet bend most certainly "nips" the U shape of the rope. The distal part of the U shape helps anchor that coil so that it can provide nip.Or would you like to claim that a bowline ceases to be a bowline as soon a rotating, high-friction load causes only the leg belonging to the U shape to be loaded?

We have been talking about all those things, and then some, on the thread about bowlines (1).

I'm not going to sift through some protracted theoretical word fight to get an answer. If you want to avoid the question, that is fine. It's off topic, and you won't change your mind anyway.

Logged

If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".

The loop or coil of the Sheet bend most certainly "nips" the U shape of the rope.The distal part of the U shape helps anchor that coil so that it can provide nip.

It is more or less, resp., of opposite-side or same-side (recommended)sheet bends, in that the mechanics of the "loop" hereare of loading-from-one-direction and not of both ends(of the loop) being pulled upon (50% & 100%, with frictionleading to equalization at some point, in normal cordage).One can suggest that the same-side ("proper") sheet bendis just a tucked version of the thief knot , to put it inperspective --of more nearly, in effect, U-2-U workings ratherthan U-2-loop. But this is getting awfully picky.

As for security and testing,some arborist did test the zeppelin eyeknot in a kernmantle("static", low-elongation something or other, 8-11mm, IIRC)rope, and found it stronger than some fig.8 he also tested("some" meaning that the exact orientation wasn't obvious).It held to a high rupture value, so obviously didn't slip.Meanwhile, we have the Dave Richards testing of variouskernmantle cordage (7mm accessory, 10.2? mm dynamic,and 12.7mm low-elongation) to show that the sheet bends(single & double) were weaker and less secure --sometimesneeding stopper knots!-- than bowlines.

Quote

Or would you like to claim that a bowline ceases to be a bowlineas soon a rotating, high-friction load causes only the leg belonging to the U shape to be loaded?

Well, this certainly points to issues in defining "knot",and why I use ' *knot* ' often, to alert one to someproblematic definitions. For, surely, in the loading above,one has an effectively different physical structure andshould expect associated behavior if so! And I do wonderif by such effective loadings those trawler hawser bowlinesget capsized; the capsized forms are undeniable, butthe path TO them is unknown to me, up for inference.

...we have the Dave Richards testing of various kernmantle cordage (7mm accessory, 10.2? mm dynamic, and 12.7mm low-elongation) to show that the sheet bends (single & double) were weaker and less secure --sometimesneeding stopper knots!-- than bowlines.

Thanks for this information. Would it be too difficult for you to cite links ?

All those "tests" you refer to, are unique, once-happened phenomena ( should we better say "miracles" ? ), or they have been verified by reasonable repetition ? Because most of the 'knot tests" I read could not have attracted any attention, if done in any field of modern science and technology... ( And, yes, I know, middle ages were different in this requirement for "plenty" of numbers... )

I believe we should first explore the ultimum strength of the many forms of "secure" bowline-like loops, before we would attempt to follow closely any - rare or not - collapse of those knots under extreme loading.